In the slotting of paper board container blanks, it is conventional to employ a slotting mechanism comprising a pair of parallel rotatable shafts on which are mounted lengthwise spaced pairs of cooperating upper and lower slotting heads between which container blanks are fed. The upper slotting head of each pair is normally provided with two radially extending slotting blades, whereas the lower head of each pair is normally formed with a peripheral groove which receives the cutting edges of the blades. During proper operation of the machine, the blades of each slotting head are successively brought into engagement with each blank such that one of the blades cuts a slot in the leading edge and the other of the blades cuts an equal length slot in the trailing edge of such blank, whereby to define flaps which are later folded over to form the top and bottom walls of the container.
When the size of the blank is varied, it is conventional to alter the angular relationship between the blades of the slotting heads in order to obtain a desired spacing between slots. The changing of the angular relationship between blades may be accomplished manually or automatically by use of apparatus of the type disclosed for instance in U.S. Pat. Nos. 3,067,643 and 3,952,637.
It is also common practice to provide machines of the type under consideration with registering apparatus by which the rotatable position of the slotting heads may be changed relative to a main drive gear or similar mechanism of the machine, as required to insure equal length slots being formed in the forward and trailing edges of a given size container. Adjustments may be accomplished manually or automatically as disclosed for instance in U.S. Pat. No. 2,121,105 in addition to the patents mentioned above.
It has also been proposed in a paper board web severing equipment, as evidenced by U.S. Pat. No. 3,742,798 to selectively retard the rotational speed of a cutoff head for the purpose of varying the length of material severed from a continuous web, during each rotational cycle of the cutoff head.